It is recognized as desirable in some instances to change from the common radiators made of steel plate for central-heating plants to those which are made of aluminum. The reasons for this are that, due to the easier formability of the aluminum, the heat-radiating surfaces can be chosen substantially larger with the same dimensions of the radiators than is the case in steel radiators. Thus, radiators made of aluminum are capable of transmitting substantially more heat while having the same dimensions than those made of steel plate, and aluminum radiators are corrosion-resistant, which does not require the lacquer finish necessary for radiators made of steel plate. Moreover, it is possible to make aluminum radiators of any desired color by the Eloxal process.
However, during the manufacture of aluminum radiators, there exist difficulties since an effective welding of aluminum parts is not possible and the elements or parts thereof must be connected in a sealed relationship by other suitable measures, for example, the elements must be press-connected to one another by steel bolts or rods which are guided in the longitudinal channels through which the heating medium flows.
If the individual elements are manufactured as a unit by pressure casting, it is necessary to connect same near their upper and lower ends. In such a design four connecting points exist for each radiator element. However, this method of manufacture is disadvantageous inasmuch as a separate casting die is needed for each size of radiator. Thus, the manufacture of radiators of different sizes becomes very expensive. A further disadvantage of such radiators is that the elements, in order to be able to be withdrawn from the dies, must be somewhat tapered, which particularly in the case of large radiators leads to an undesirable shape of the elements. The elements are open on one side and must subsequently be closed in a suitable manner. In addition aluminum, in order to accept spraying, must contain iron, which, however, again excludes the Eloxal process.
To avoid the disadvantage of needing a plurality of pressure casting dies, it has further been suggested, to make the central parts of the radiator elements of extruded profiles and to provide same with specially manufactured, extruded head pieces at their upper and lower ends. In this manner radiators having various heights can be produced with equal head pieces by selecting various lengths of the center pieces of the radiators, without necessitating for each size of the elements a separate casting die. Of course, in such case it is not only necessary to connect the elements with one another, but also the head pieces must be connected sealingly with the center parts of the elements. Thus, each element of the radiator has six connecting points, which, in order to achieve the required seal, is technologically very difficult and expensive to manufacture.
Thus the basic purpose of the invention is to produce an aluminum radiator, which avoids the disadvantages existing in the known aluminum radiators which can be made in different sizes, without requiring a plurality of pressure casting dies and in which, further, the individual elements are connected in a technologically simple manner.